An electrician leans an extension ladder against the outside wall of a house so that it reaches an electric box 35 feet up. The ladder makes an angle of 79^{\circ} ∘ with the ground. Find the length of the ladder. Round your answer to the nearest hundredth of a foot if necessary.

In the area that she observed, the water level fell 13.64mm over 6.4 years, for an average annual rate of change of:
-13.64 ÷ 6.2 = -2.2 mm/ year. 

The difference between how much average water levels rose and how much water levels in her part of the river fell is:
1.8 -(-2.2) = 4 mm/year

During the 6.2 year period: 
4 mm/year * 6.2 = 24.8 mm