With explanation and numbers please :)

Ralph Corporation manufactures two products, I and II, from a joint process. A production run costs $18,000 and results in 500 units of I and 2,000 units of II. Both products must be processed past the split-off point, incurring separable costs of $8 per unit for I and $10 per unit for II. The market price per unit is $40 for I and \$20 for II. (1) Determine the amount of joint costs is allocated to Product I using the physical unit methods (2) Determine the amount of joint costs is allocated to Product I using the net realizable value method. (3) Determine the amount of joint costs is allocated to Product I using the constant gross margin percentage method