77.

1. $\approx 550\text{ft}$

2. $\approx 140\text{ft}$

3. 547 ft; 139 ft

79. 19

81. 25

83. Square with 20-unit sides; maximum area: 400 square units

85. Dimensions: $75\text{m}\times 100\text{m};$ area: $7500{\text{m}}^2$

87. 38

89. 28 students; maximum revenue: $1568

91.

1. $h(t)=-0.8t^2+8t+5$ (meters)

2. 5 sec

93.

1. 64 ft

2. After 4 sec

95. Dimensions of the rectangle: $\text{height}={\displaystyle \frac{18}{\pi +4}}\text{ft};\text{ width}={\displaystyle \frac{36}{\pi +4}}\text{ft}$

97.

1. (59, 36.81)

2. 120 ft

3. 37 ft

4. 9 ft

5. 113.6 ft

99.

1. $f(x)=0.029{(x-3.79)}^2+1.09$

2. At $x=3.79\approx 4(\text{year }2010)$, which fits the original data

3. $f(5)=1.14$ million