The answer would be 4 as it more than 40 degrees whoch will allow to it record
Sorry this got to you super late. At least others looking for the answer can find it.
P=15.5 would be the answer
Perfect square is
a²+2ab+b²
so just take the square root of the end ones and add then double to get middle term
A.
m+10=10m, doubled is 20m
nope
B.
m+5=5m, doubled is 10m, yep
C.
m+2√15=fancy thing that won't get to 36m
D.
m+12=12m, doubled is 24m, yep
B and D