How will the court decide whether Griffin is entitled to testify about the conversation?

Richard Griffin and three other men owned a grain company called Bearhouse, Inc., which needed to borrow money. First National Bank was willing to loan $490,000, but it insisted that the four men sign personal guaranties on the loan, committing themselves to repaying up to 25 percent of the loan each if Bearhouse defaulted. Bearhouse went bankrupt. The bank was able to collect some of its money from Bearhouse’s assets, but it sued Griffin for the balance. At trial, Griffin wanted to testify that before he signed his guaranty, a bank officer assured him that he would only owe 25 percent of whatever balance was unpaid, not 25 percent of the total loan. How will the court decide whether Griffin is entitled to testify about the conversation?