I think is D
5^-2*25^-1
5^-2*5^-2
5^-4
1/5^4
1/625
0,0016, 5^-4
You need to divide 313.5/12.5=25.08 so the width is 25.08 feet
well, a WHOLE is 1, in this case is 8/8, that'd be a whole.
so Billy does 1/8 in 15 minutes, well, there are 8/8, so do the whole recipe that'd be 8 * 15 minutes, or 120 minutes, or 2 hours.
or you can see it this way, 1/8 is 15 minutes, since there are eight 1/8's, then it'd take 15+15+15+15+15+15+15+15 minutes.
The answer is 82 and your welcome
If the remaining 4 letters can be anything, you have 2*26^4 = 913,952 possible 5-letter ham radio call signs.