$\text{A}$ and $\text{B}$ start at the same time from the same place towards their office. If the speed of $\text{B}$ is $5/6$ times of $\text{A’s}$ speed, then he reaches the office $\text {1 hour 15 minutes}$ after $\text{A}$. Find the time taken by $\text{A}$ to reach the office ?
- $\text {5 hours 30 minutes}$
- $\text {6 hours 15 minutes}$
- $\text {6 hours 45 minutes}$
- $\text {7 hours 30 minutes}$