assume 75 put option selling 8 12 while 65 put option same expiration date

Assume a 75 put option is selling for 8 1/2 while a 65 put option, with the same expiration date is selling for 3 1/4. Using these options, construct a bull spread and workout the profit and loss( ignore commissions) if the stock price equals 60, 70, 80, or 90 at expiration. When would it be appropriate to use a bull spread?