Edison wants to purchase a new computer and go to the Caribbean for spring break. The computer is priced at $1,299, and the vacation is priced at $800. He has only $1,574 in his checking account, so he cannot afford to purchase both. After much thought, Edison buys the computer and writes a check for $1,299. Edison can easily determine that the price of the computer is more than the price of the vacation. is htis a medium of exchange?