Please help me with these three questions. They deal with coefficient of friction

1) A car rounds a turn of radius 25m at a speed of 20m/s. Find the coefficient of friction neccessary to keep the car on the road

2) A man is attempting to slide a piece of furniture weighing 750N long a floor. Ifhe exerts a force of 75N along a rope and angle of 35 degrees and the object does not move, what is the minimum value for te coeficient of friction?

3) Consider a block on a plane inclined at an angle of 30 degres. If the block weights 950N, what coefficient of friction is neccessary to hold it stationary?