The problem says that the two shapes are congruent. This means they have the same length and angle measurements. So, in order to find out what OP is, you have to find its corresponding part which is WX. The measurement of WX is 35 yd which means that the measurement of OP is also 35 yd because they are corresponding side lengths therefore being the same.
The formula for this is . If the diameter is 8 the radius is 4, so filling in accordingly we have and which is and when you multiply in 3.14 you get that A = 401.92 or B above.