Suppose that we are given a relation schema r with four attributes, abcd, and the set of fds f = { ab  c, bc  d, d  a }. assuming those are the only dependencies that hold for r, answer the following questions (justify briefly your answers): (a) is ac a key of r? (b) is ab a key of r? (c) what is a prime attribute? is attribute a a prime attribute? (d) is r in 3rd normal form (3nf)? (e) is r in boyce-codd normal form (bcnf)

The three logical operators used to write compound conditions are "and," "or," and "not." a: true b: false

Assume that to_the_power_of is a function that expects two int parameters and returns the value of the first parameter raised to the power of the second parameter. write a statement that calls to_the_power_of to compute the value of cube_side raised to the power of 3 and that associates this value with cube_volume.

Assume that there is a 4% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on three independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?