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Discrete mathematics question

Q5. The Fibonacci numbers for n=0,1,... are defined as follows. fib (0) = 0; fib (1) = 1; fib (n) = fib (n-1) + fib (n - 2); Consider the following piece of code that calculates the Fibonacci numbers. int fib (int n) { if (n is 0) return 0 else if (n is 1) return 1 else return tib (n-1) + fib (n - 2) What is the worst-case complexity of the above code