Contract the expressions given in Problems 25-28. That is, use the properties of logarithms to write each expression as a single logarithm with a coefficient of 1.

a. \(\log 2+\log 3+\log 4\)

b. \(\log 40-\log 10-\log 2\)

c. \(2 \ln x+3 \ln y-4 \ln z\)