Answer:
50 Minutes.
Explanation:
The function c approximates the total number of calls made after m minutes since the start of the phone tree.
![c(m)=(2)/(3)* (3^{(m)/(10)}-1)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/gfk3bad439eeuuy5mpka8ybc7a5w966xkl.png)
We need to find the number of minutes after which the total number of calls will 363.
Substitute c(m)=363 in the given function.
![363=(2)/(3)* (3^{(m)/(10)}-1)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/bqzuk9q9ddn7b6lmazoogltqg34ebwe5r7.png)
Multiply 3/2 both sides.
![363* (3)/(2)=(3^{(m)/(10)}-1)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/clpc6v2q01hrqmtzjok8vo0padvlz8pi6e.png)
![242=3^{(m)/(10)}-1](https://img.qammunity.org/2021/formulas/mathematics/middle-school/4n5hzofccl24vbxyc2vfwopvt5txb9dtdc.png)
Add 1 on both sides.
![243=3^{(m)/(10)}](https://img.qammunity.org/2021/formulas/mathematics/middle-school/hsq3obfr4amc04o6hljh2wr6280zf10m8w.png)
![3^5=3^{(m)/(10)}](https://img.qammunity.org/2021/formulas/mathematics/middle-school/qod8zx2eqlccrfgbeitj4tbxpqztqpacfx.png)
On comparing both sides we get
![5=(m)/(10)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/qf1anf0y0luxlznug1utys6r2ozvv164uj.png)
Multiply both sides by 10.
![50=m](https://img.qammunity.org/2021/formulas/mathematics/middle-school/4i7ctjgehlticc5ptbsgoiyqdc5895i9qs.png)
Therefore, the total number of calls will 363 after 50 minutes since the start of the phone tree.