At the end of a snow storm, Savannah saw there was a lot of snow on her front lawn. The temperature increased and the snow began to melt
at a steady rate. The depth of snow on Savannah's lawn, in inches, can
be modeled by the equation S -1.5t + 15, where t is the time, in
hours, after the snow stopped falling. What is the slope of the equation
and what is its interpretation in the context of the problem?