For a student's first semester at college, the college charges 105 dollar per credit-hour plus a one-time $\$ 50$ admissions fee. The cost $C$ (in $\mathrm{S}$ ) for the first semester is given by $C=105 h+50$ where $h$ is the number of credit-hours taken. If a student is billed 1415 dollar, how many credit-hours is she taking?