Some help with an Excel formula please.

The formula is for working out time costs

Cell A1 will be marked with an X or left blank

So when time is place in cell C1 the hourly rate will be calculated at one of two rates, with the X in cell A1 deciding which hourly rate to apply.

So if I place the formula =IF(A1>0, (C1*24)*100) in D1, mark A1 with a X and enter 10:00 in C1 I get the correct answer of £1000 in D1.

What I want to do is expand the formula (or find a better way) so that in D1 if A1 has no X, it will calculate the costs at £50 per hour and if it has an X, calculate the costs at £100.

Thanks