Three Dimensional Geometry

Consider a pyramid OPQRS located in the first octant (x≥0,y≥0,z≥0) with O as origin, and OP and OR along the x-axis and the y-axis, respectively. The base OPQR of the pyramid is a square with OP= 3. The point S is directly above the mid-point T of diagonal OQ such that TS = 3. Then-