A power calculation has shown that if = 8, the power of a test of H0

Question:

A power calculation has shown that if μ = 8, the power of a test of H0 :μ ≥ 10 versus H1 :μ < 10 is 0.90. If instead μ = 7, which one of the following statements is true?
(i) The power of the test will be less than 0.90.
(ii) The power of the test will be greater than 0.90.
(iii) We cannot determine the power of the test without knowing the population standard deviation σ?