Chicago Cleaning Services Provides Nightly Janitorial Services at a Monthly

Chicago Cleaning Services provides nightly janitorial services at a monthly rate of $300.Customers have three payment options:
$\begin{array}{ll}\text { Month-by-month payments } & \$ 300 \\\text { One year advance payment } & 3,360(\$ 280 \text { per month) } \\\text { Two year advance payment } & 6,480(\$ 270 \text { per month) }\end{array}$
If Chicago Cleaning is a cash basis taxpayer:
I.All cash payments are taxable when they are received.
II.One-year advance payments may be deferred: $280 would be included in income for each month of service provided.

A) Only statement I is correct.
B) Only statement II is correct.
C) Both statements are correct.
D) Neither statement is correct.