Pasta   Tofu
Protein         8g     16g
Carbohydrates  60g     40g
Vitamin C       2g      2g
Cholesterol    60mg    50mg

Let introduce variable 'x':

Let 'x'  be the number of days of the month James eats pasta for lunch;

then the number of days James eats tofu for lunch is (30-x)   //  assuming 30 days in a month.


So, the problem is to minimize 

    H = 60x + 50(30-x)    (1)


under restriction

     8x + 16(30-x) >= 200,    (2)   (protein restriction)

    60x + 40(30-x) >= 960,    (3)   (carbohydrate restriction)

     2x + 2(30-x)  >=  40     (4)   (vitamin C restriction)

     0 <= x <=  30.           (5)


Let' simplify expression (1) and inequalities (2) - (5).


In simplified form, we want to minimize

    H = 10x + 1500            (1')

under restrictions

    -8x +  480 >= 200,  which we transform to  8x <= 280,    which we transform  x <= 35;     (2')

    20x + 1200 >= 960,  which we transform to  20x >= -240,  which we transform  x >= -12;    (3')

            60 >=  40,                                                                        (4')

     0 <= x <= 30.             (5')


Looking at these transformed restrictions, we see that in the domain  0 <= x <= 30 they (the restrictions)
are held at any value of x.


So, if we want to minimize (1'), we should take x = 0.


The solution is that James should not eat pasta and should eat tofu every day for lunch.

Indeed, with the given input data, it is clear that James can eat either pasta or tofu every day

    (a)  consuming protein will be more than 200 grams in either case;

    (b)  consuming carbohydrate will be more that 960 grams in either case;

    (c)  consuming vitamin C will be more than 40 grams in either case.


So, in reality, these three restrictions are not the restrictions, at all.


Therefore, if James wants to minimize cholesterol, he should eat tofu every day,
since tofu provides lesser cholesterol.