A Hot, Wet Summer Is Causing a Mosquito Population Explosion $2,100 + 7 e ^ { 0.7 t }$

Short Answer

A hot, wet summer is causing a mosquito population explosion in a lake resort area. The number of mosquitoes is increasing at an estimated rate of $2,100 + 7 e ^ { 0.7 t }$ per week (where $t$ is measured in weeks). By how much does the mosquito population increase between the 4th and 6 th weeks of summer?