I'm mostly confused on the semi annual interest. in these three questions.

2. A loan of $3000 is to be repaid in four equal semiannual (every 6 months) payments. If the annual interest rate is 8% compounded semiannually, how much is each payment? 3. A machine costs $30,000 and has a 6-year useful life. At the end of the 6 years, it can be sold for $9,000. If annual interest is 8%, compounded semiannually, what is the equivalent uniform annual cost of the machine? 4. A machine has a first cost of $100,000, an annual operation and maintenance cust of $4000, a life of 8 years, and a salvage value of $20,000. At the end of Year 4, it requires a major service, which costs $10,000. If the annual interest rate is 8%, what is the equivalent uniform annual cost of owning and operating this particular machine