At node P in a complex network, currents in five branches are described using the convention: positive value means the current is toward the node. The measured values are I1=+1.8A, I2=−0.5A, I3=+0.9A, and I4=+0.4A. Determine I5 under the same sign convention so that the current balance at the node is satisfied.
a) +3.1A
b) −2.6A
c) +2.6A
d) −3.6A