Final answer:
It will take approximately 13 months to save an emergency fund sufficient to cover three months' worth of living expenses at $3,900 per month, with a monthly saving of $900.
Step-by-step explanation:
To determine how long it will take to fully fund an emergency fund, we first need to calculate the total amount needed, which is the living expenses for three months. With a monthly expense of $3,900, the total for three months would be $3,900 × 3 = $11,700.
Since the student is saving $900 each month, we can divide the total needed by the monthly savings to find the number of months required: $11,700 / $900 ≈ 13 months. Therefore, it will take approximately 13 months to save enough for a three-month emergency fund.