How to formulate in excel solver?

Consider a distribution planning problem with 3 warehouses (W1 to W3) and 12 retailers (R1 to R12). Warehouse capacity is 5000, 5000, and 3000 respectively for W1 to W3. Retailer demands are (from R1 to R12): 650, 400, 850, 1900, 3100, 250, 350, 400, 500, 400, 1350, and 450. The unit shipping costs (in dollars) between the warehouses and retailers is given in the table below. Determine the optimum distribution plan that will minimize the total cost (formulate and solve, e.g., using Excel solver). R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 W1 3.50 3.60 4.30 4.80 3.10 3.70 3.80 3.80 3.70 3.80 4.50 3.90 W2 4.30 4.90 3.80 3.70 4.40 3.90 4.10 4.00 4.30 4.75 3.00 4.90 W3 3.00 3.90 3.30 4.20 3.40 3.10 3.50 2.80 3.10 3.50 3.80 4.10