For a put option on a stock expiring in 6 months:

• The current price of the stock is 50.

• The strike price is 55.

• The continuously-compounded dividend rate is 0.02.

• The continuously-compounded risk-free interest rate is 0.06.

  The option is modelled with a one-period binomial tree. The replicating portfolio for the option consists of a long bond with a current value of 40 and -0.6 shares of the stock.

  Determine u, the multiplier used for the upper node of the binomial tree.