Gina will give 4 clothing for 1 food while Norman is willing to accept 1 clothing for 1 food.
If they settle on 2 or 3 units of clothing for one unit of food they will both be better off. Let’s
say they settle on 3 units of clothing for 1 unit of food. Gina will give up 3 units of clothing and receive 1 unit of food so her final allocation is 2F and 5C. Norman will give up 1 food and gain 3 clothing so his final allocation is 5F and 5C. Gina’s MRS will decrease and Norman’s will increase, so given they must be equal in the end, it will be somewhere between 1 and 4, in absolute value terms. So a possible value for both individual’s MRS at the efficient solution is 2.5.