Radiation Measurement?

I know how to do the calculations for this problem but webassign keeps telling me I have my significant figures wrong for question b and c. Could anyone help me figure out what I am doing wrong with the significant figures? Your response is greatly appreciated.

a) A patient receives 40. mrads in a chest X ray. What is that amount in grays?
my ans: 4.0e-4 (correct)
(b)What would be the dose in millirems?(assume xray has same factor as gamma)
(c) Suppose a person absorbed 40. millirads of alpha radiation. What would be the dose in millirems?

My calculations for b) rem=rad * factor, so 40*1=40
My calculations for c) 40 * 20= 800

I can only guess...but maybe the problem is that you don't write b and c in scientific notation.
Maybe webassign thinks that 800 has three significant figures, while 8.0 e+2 has only two.
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