Find Minimum and Maximum values

[Inigo Montoya]

I have a form that has people enter an amount, and it calculates a discount for the invoice and displays it, as well as total of all invoices, number of invoices, and average invoice amount. I need it to also display the smallest and largest invoices. I am still quite new to C#, so any hints would be greatly appreciated. Here's the code I have so far, not sure how to start on the last part, looking into using Math.Max and Math.Min.

public partial class frmInvoiceTotal : Form
	{
		public frmInvoiceTotal()
		{
			InitializeComponent();
		}

        int numberOfInvoices = 0;
        decimal totalOfInvoices = 0m;
        decimal invoiceAverage = 0m;
        
        private void btnCalculate_Click(object sender, EventArgs e)
		{
			decimal subtotal = Convert.ToDecimal(txtEnterSubtotal.Text);
			decimal discountPercent = .25m;
            decimal discountAmount = Math.Round(subtotal * discountPercent, 2);
			decimal invoiceTotal = subtotal - discountAmount;

            txtEnterSubtotal.Text = subtotal.ToString("c");
            txtDiscountPercent.Text = discountPercent.ToString("p1");
			txtDiscountAmount.Text = discountAmount.ToString("c");
			txtTotal.Text = invoiceTotal.ToString("c");

            numberOfInvoices++;
            totalOfInvoices += invoiceTotal;
            invoiceAverage = totalOfInvoices / numberOfInvoices;

            txtNumberOfInvoices.Text = numberOfInvoices.ToString();
            txtTotalOfInvoices.Text = totalOfInvoices.ToString("c");
            txtInvoiceAverage.Text = invoiceAverage.ToString("c");

            txtEnterSubtotal.Text = "";
			txtEnterSubtotal.Focus();
		}

        private void btnClearTotals_Click(object sender, System.EventArgs e)
        {
            numberOfInvoices = 0;
            totalOfInvoices = 0m;
            invoiceAverage = 0m;

            txtNumberOfInvoices.Text = "";
            txtTotalOfInvoices.Text = "";
            txtInvoiceAverage.Text = "";

            txtEnterSubtotal.Focus();
        }

        private void btnExit_Click(object sender, EventArgs e)
		{
			this.Close();
		}

        private void label10_Click(object sender, EventArgs e)
        {

        }

	}
}