A) to find the difference you have to subtract one from the other (53-(-41)=91)
b) 15
Answer:
radius 12 units = 452.16 units²
diameter 16.8 units = 221.5584 units²
radius 3.4 units = 36.2984 units²
diameter 10 units = 78.5 units²
Formula for area of circle: 
Note for probability, if it will never happen the P = 0. If it must happen P = 1.
So certain to happen:
C. P=1
I think this is the answer to your question And also the solution