Calcium is essential to tree growth because it promotes the formation of wood and maintains cell walls. In 1990, the concentration of calcium in precipitation in a certain area was 0.15 milligrams per liter (mgIL). A random sample of 10 precipitation dates in 2007 results in the following data table. Complete parts (a) through (c) below. E Click the icon to view the data table. (a) State the hypotheses for determining if the mean concentration of calcium precipitation has changed since 1990. Ho: [.1 = 0.15mg/L H1: u # 0.15mg/L (b) Construct a 90% condence interval about the sample mean concentration of calcium precipitation. The lower bound is The upper bound is :|. (Round to four decimal places as needed.)