Answer
a). $2.19mg$ at the top of the loop.
b). $4.19mg$ at the bottom of the loop,
Work Step by Step
a). $F_{N}=mg(-1+\frac{250^{2}}{2000\times9.8})=2.19mg$ at the top of the loop.
b). $F_{N}=mg(1+\frac{250^{2}}{2000\times9.8})=4.19mg$ at the bottom of the loop.