Four identical resistive strain gauge factor of 2.0 used in a wheatstone bridge as shown in the figure below. Only one of the strain gauges R${_S}{_E}{_N}{_S}{_E}$ changes its resistance due to strain. If the output voltage V${_O}{_U}{_T}$ is measured to be1 m V, the measured of strain, in units of microstrain, is
- $1$
- $10$
- $100$
- $1000$