Step 1: Let the total salary be \( x \).
Step 2: The expenditures are given as:
The total expenditure is:
\[ \frac{2}{5}x + \frac{3}{10}x + \frac{1}{8}x \]
Step 3: Finding a common denominator for the fractions:
\[ \frac{16}{40}x + \frac{12}{40}x + \frac{5}{40}x = \frac{33}{40}x \]
Step 4: The remaining amount is:
\[ x - \frac{33}{40}x = \frac{7}{40}x \]
Given that this remaining amount is Rs. 1400, we set up the equation:
\[ \frac{7}{40}x = 1400 \]
Solving for \( x \):
\[ x = \frac{1400 \times 40}{7} = 8000 \]
Step 5: The expenditure on food is:
\[ \frac{3}{10}x = \frac{3}{10} \times 8000 = 2400 \]
Thus, the correct answer is Rs. 2400.