A ball is dropped from the top of a building. The ball takes 0.5 s to fall past the 3 m length of a window some distance from the top of the building. If the velocities of the ball at the top and at the bottom of the window are \[{{v}_{T}}\] and \[{{v}_{B}}\] respectively, then \[(take\text{ }g=10\text{ }m/{{s}^{2}})\]

• A. \[{{\text{v}}_{\text{T}}}\text{+}{{\text{v}}_{\text{B}}}\text{=12m}{{\text{s}}^{-1}}\]
• B. \[{{\text{v}}_{\text{T}}}-{{\text{v}}_{\text{B}}}=4.9\text{m}{{\text{s}}^{-1}}\]
• C. \[{{\text{v}}_{\text{B}}}{{\text{v}}_{\text{T}}}\text{=1m}{{\text{s}}^{-1}}\]
• D. \[{{\text{v}}_{\text{B}}}\text{/}{{\text{v}}_{\text{T}}}\text{=1m}{{\text{s}}^{-1}}\]