Answer:
4 meters
Explanation:
Given
S models the ice sheets thickness (in meters) after t weeks. S= -0.25t+4
this model represent that
thickness of ice sheet will be -0.25t+4 meters
thus
for example after 1 week
thickness of ice sheet will be found by putting t = 1
thickness of ice sheet after 1 week = -0.25*1+4 = -0.25 + 4 = 3.75 meters
______________________________________________
we have to find thickness at the beginning of spring
at the beginning there will be zero weeks passes
thus,
we can find thickness at beginning of street by putting t = 0
thickness of ice sheets at the beginning of spring = -0.25*0+4
thickness of ice sheets at the beginning of spring = 0+ 4 = 4 meters