To calculate the amount of money Marcus has for entertainment, we can use the following formula:
\[ \text{Amount for Entertainment} = \text{Net Income} \times \left(\frac{\text{Percentage for Entertainment}}{100}\right) \]
In this case, Marcus has a net income of $4200 and allocates 5% for entertainment.
Now, we can calculate this:
\[ \text{Amount for Entertainment} = 4200 \times \left(\frac{5}{100}\right) \]
\[ \text{Amount for Entertainment} = 4200 \times 0.05 \]
\[ \text{Amount for Entertainment} = 210 \]
So, Marcus has $210 for entertainment each month.