If a • b = b, what must the value of a be?

I'm being volume of cylinder with 13 in. radius and 30 in height answer choices in pic

Question 3 of 30 paul buys fruit to make smoothies. he buys 3.78 pounds of apples, 2.12 pounds of peaches, and 4.45 pounds of oranges. paul rounds each weight to the nearest tenth of a pound. about how many pounds of fruit did paul buy? (a) 10.5 pounds (b) 10.2 pounds (c) 10.4 pounds (d) 10.0 pounds 30 points

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?