D. 289
Take the formula:
K=5/9(Fahrenheit-32)+273
Plug in Fahrenheit
K=5/9 (60-32)+273
From here it is simple math and you can plug it into your calculator getting 288.5555556 and round to 289
Explanation:
q= n e
6 × 10^-11 = n (1.6 × 10^-19)
n = 6×10^-11 / 1.6 × 10^-19
n= 3.75 × 10⁸ electrons
D. Using a fixed-pulley system
To solve this exercise it is necessary to take into account the concepts related to Tensile Strength and Shear Strenght.
In Materials Mechanics, generally the bodies under certain loads are subject to both Tensile and shear strenghts.
By definition we know that the tensile strength is defined as

Where,
Tensile strength
F = Tensile Force
A = Cross-sectional Area
In the other hand we have that the shear strength is defined as

where,
Shear strength
Shear Force
Parallel Area
PART A) Replacing with our values in the equation of tensile strenght, then

Resolving for F,

PART B) We need here to apply the shear strength equation, then



In such a way that the material is more resistant to tensile strength than shear force.
The answer is reflection.
The drawing is simple but illustrates the concept beautifully.