Hey guys. I have attached some questions about Canadian Tax. The answers are correct, however, I do not know WHY those are the answers. If anyone can walk me through on why these are the answers, I would really appreciate it.

D loaned $200,000 to a small business corporation four years ago. By the end of the current year, it was established none of the loan would be repaid due to financial difficulty. D claimed a capital gains deduction of $80,000 last year. What is the maximum allowable business investment loss (ABIL) for the current year? 20,000 5% B sold shares of a qualified small business corporation (QSBC) in the current year realizing a taxable capital gain of $360,000. B has a net capital loss of $100,000 carried over from last year that he wants to deduct in the current year. B deducted an allowable business investment loss (ABIL) of $80,000 last year. B's cumulative net investment loss (CNIL) account at the end of the current year should be $0. B claimed a capital gains deduction of $200,000 three years ago. What is B's maximum capital gains deduction for the current year? 180,000 5% C Inc. is a Canadian-controlled private corporation carrying on business in Canada. The net fair market value of the assets and liabilities of C Inc. is estimated to be $154,000 (Cash $3,000; Accounts receivable $60,000; Furniture and equipment $26,000; Long term investments $30,000; Goodwill $40,000; Liabilities $5,000). The shares of C Inc. have been owned by Mrs. Cee for the past three years during which time the relative values of the assets and liabilities have remained constant. Is C Inc. a qualified small business corporation (QSBC)? No Individual H received eligible dividends totaling $20,000 in the current year. What is the amount of the federal dividend tax credit? 4,143 3.15 Individual K donated $4,000 to a Canadian registered charity. K's taxable income is $150,000. What is the amount of the federal donation tax credit? 1,132 5% N's medical expenses paid during a 12-month period ending in the current year totaled $3,600. The medical expenses for N's 20-year-old son paid during the same 12-month period totaled $1,800. For the current year, N had net income of $120,000 and the son had net income of $6,000. What is the maximum federal medical expense credit? 447 1.05 P received Old-age security pension (OAS) payments totaling $6,850 in the current year. No tax was withheld. P's net income for the current year is $90,000 before adjusting for any OAS repayment. What is the amount of the OAS repayment (Part 1.2 tax) for the current year? 2,437 1.05