A manufacturing process has $2$ stations, A and B$,$ that are ordered in sequence. At each station, two tasks are performed one after the other. Suppose the time $($in seconds per unit$)$ it taks for a single person to perform each task is given below. Station A has $1$ worker and Task $1$ takes $20$ seconds, Task $2$ takes $25$ seconds. Station B has $2$ workers and Task $1$ takes $40$ seconds, Task $2$ takes $40$ seconds. If Station A has $1$ worker and station B has $2$ workers to do the different tasks, the capacity of this process under steady state $($in units per hour$)$ is: a$.90/$hour b$.80/$hour c$.180/$hour d$.45/$hour e$.$ none of the above