Bert Johnson, a sole proprietor with no employees, has a Keogh profit sharing plan to which he may contribute 25% of his annual earned income. For this purpose, "earned income" is defined as net self-employment earnings reduced by the:

a. Deductible Keogh contribution.

b. Self-employment tax.

c. Self-employment tax and one-half of the deductible Keogh contribution .

d. Deductible Keogh contribution and one-half of the self-employment tax.