9. By means of strain gages, the flexural stresses are found to be -12,000 psi at A and
+4000 psi at B. Assuming the elastic limit of the material has not been
exceeded, find the flexural stress at the bottom of the beam.
a. 6000 psi
b. 8000 psi
c. 9000 psi
d. 10,000 psi
e. 12,000 psi