A synaptic cleft is a small gap (typically about 20 nm in width) between two nerve cells across which chemical signals are exchanged. If you assume that one cell emits a neurotransmitter such that its concentration right outside of that cell is 100μM, and that receptors at the other cell absorb every molecule that reaches it, how many molecules flow per second across the cleft? Assume a surface area of the cleft of 1μm² and a diffusion coefficient of 2×10⁻¹¹ m²/s. How long does it take for one molecule to traverse the cleft and how does that time relate to how fast such a synapse can transmit signals?