Two friends work at different buildings on opposite sides of the city. they would like to meet for coffee after work someplace in between both locations. one friend works 9 blocks west and 6 blocks south of the center of town. the other friend works 9 blocks east and 4 blocks north of the center of town. which restaurant is closest to the midpoint of the two locations?
a. restaurant casa, which is 1 block south of the center of town
b. pizza di franco, which is 9 blocks north and 5 blocks west of the center of town
c. cafe rosa, which is 2 blocks north and 2 blocks east of the center of town
d. 7th st. market, which is 2 blocks south and 3 blocks east of the center of town