Carolina is mowing lawns for a summer job. For every mowing job, she charges an initial fee plus $\$6$ for each hour of work. Her total fee for a $4$-hour job, for instance, is $\$32$. Let $F(t)$ denote Carolina's fee for a single job $F$ (measured in dollars) as a function of the number of hours $t$ it took her to complete it. **Write the function's formula.** $F(t)=$ [[☃ expression 1]]