If A1 = 6/1/2006, can B1 = the number of days in June w/o using a VLOOKUP?

Im trying to embed a couple of conditions in an IF statement and i don't
know where to begin.

I have a fixed volume of 500/day; July = 31 days; total 15500 for july.

I need to charge .442 for the first 10000 per unit, 1.327 for the next 100
units, 1.098 forthe next 140, and .9255 for the remaining units, which in
this case are 5260.

I made A1 = 500x31 (15500) and then have the formula point at it.

How can i make C1 read A1 and then give me the correct output for that volume?

Thank you for all your help in advance.