a. The computer should be repaired soon. You better start repairing it now.
b. The computer ought to be repaired soon. You better start repairing it now.
c. The computer must be repaired soon. You better start repairing it now.
Are all of the above grammatically correct and meaningful?
Is there a difference in the meanings?
Here 'should' and 'ought to' are supposed to express necessity and not likelihood.
I think they all work and (c) is more emphatic.