4. Matthew had to retire early because of a job-related injury. During the current year, he receives $10,000 in Social Security benefits. In addition, he receives $7,000 in cash dividends on stocks that he owned and $8,000 in interest on tax-exempt bonds. Assuming that Matthew is single, what portion of his social security is taxable? a. He receives no other income? b. He also receives $11,000 in unemployment compensation? c. He sells some land for $80,000? He paid $45,000 for the land.