Footballs are made using a four$-$step process. In the stamping step, the leather is cut and stamped with the appropriate logo$.$ This takes $15$ seconds per football, and the process is staffed with six people. In the stitching step, the four panels are sewn together. This takes $25$ seconds per ball, and the process is staffed with ten people. In the bladder insertion step, a rubber inflatable bladder is inserted inside the sewn panels and is partially inflated. This step takes $20$ seconds per ball and is performed by eight people. The final step, lacing, is completely manual, taking $40$ seconds per ball. What is the minimum number of workers to use at lacing to ensure that the overall process capacity is $1,440$ footballs per hour?

a$.12$

b$.18$

c$.16$

d$.14$