Area (A) $= 5\,\mathrm{cm} \times 8\,\mathrm{cm} = 40\,\mathrm{cm}^2$$= 40 \times 10^{-4}\,\mathrm{m}^2 = 4 \times 10^{-3}\,\mathrm{m}^3$The loop lies in the x-y plane, so its area vector is along the z-direction $(\hat{k})$.The magnetic field is given as $\vec{B} = 2.0\,\hat{k}$.Since $\vec{B}$ and $\vec{A}$ are parallel, $\theta = 0^{\circ}$ and $\cos\,\theta = 1$.$\phi = B \times A = 2.0 \times (4 \times 10^{-3}) = 8 \times 10^{-3}\,\mathrm{Wb}$The total magnetic flux is $8 \times 10^{-3}\,\mathrm{Wb}.$