Girish Shambu and Delores Reisel are teammates at a discount store; their new job is assembling bicycles for customers. Assembly of a bike has a learning rate of $75\%.$ They forgot to time their effort on the first bike, but spent $5$ hours on the second. They have $6$ more bikes to do$.$ Determine approximately how much time will be $($was$)$ required for:

The $1$st unit $=$