What problems can be caused by volcanic eruptions?

Volcanic eruptions can cause significant damage. The magma that becomes lava can totally change a landscape. It will destroy all plants it touches. Some will create layers of hardening lava. This lava may not even be hard yet. Volcanoes can destroy pretty much every material used to build towns and cities. Though plants die from volcanic eruptions, they will grow back by using the ash underground.

Quizlet has the answer

H=   2(area/a+b)h= 2(144/a+b)h= 2(144/18+18)h= 2(144/36)h= 2(4)h=8