On December 31, 2006, the Grand corporation received a cash payment of $30,000 in advance on the production of a custom machine to be delivered in March 2007. This transaction will result in which of the following on the December 31st, 2006 financial statement?

a. no effect on liabilities

b. a decrease in assets of 30k

c. an increase in revenue of 30k

d. an increase in liabilities of 30k