To find the height of the infant son, we need to calculate \( \frac{1}{4} \) of the father's height, which is \( 6 \frac{2}{3} \) feet.
First, convert \( 6 \frac{2}{3} \) to an improper fraction:
\[ 6 \frac{2}{3} = \frac{20}{3} \text{ feet} \]
Now, calculate \( \frac{1}{4} \) of \( \frac{20}{3} \):
\[ \frac{1}{4} \times \frac{20}{3} = \frac{20}{12} = \frac{5}{3} \text{ feet} \]
Now, convert \( \frac{5}{3} \) back to a mixed number:
\[ \frac{5}{3} = 1 \frac{2}{3} \text{ feet} \]
Therefore, the height of the son is:
1 2/3 ft (1 and 2 thirds ft).