Accounting - Incremental Analysis

Im having problems with this question, any help would be great.

Benson Inc. produces three separate products from a common process costing $100,000. Each of the products can be sold at the split-off point or can be processed further and then sold for a higher price. The cost and selling price data for the recent period are as follows:

Product 12:

Sales Value at split off point = $50,000

Cost to process further = $100,000

Sales value after further processing = $190,000

Product 14:

Sales Value at split off point = $10,000

Cost to process further = $30,000

Sales value after further processing = $35,000

Product 16:

Sales Value at split off point = $60,000

Cost to process further = $150,000

Sales value after further processing = $220,000

a) Determine the total net income if all products were sold at the split off point

b) Determine the total net income if all products were sold after further processing

c) Using incremental analysis, determine which products should be sold at the split-off point and which should be processed further

d) Determine the total net income using the results in c) and explain why the net income is different from that determined in b)

For a) would the net income just be 50,000+10,000+60,000 = 120,000 - 100,000 in costs which would equal a net income of $20,000?

For b) would the net income be 190,000+35,000+220,000 = 445,000 in sales minus 100,000+30,000+150,000+100,000 = 380,000 in costs which gives a net income of $65,000?

If anyone could check my answers and help me out with parts c and d that would be great. Thanks