look-up that takes a dictionary and a key and evaluates to the value associated with the specified key in the dictionary. A dictionary is a list of key, value pairs. Values in a dictionary are retreived not by index or value, but by the key that they are associated with. (Think of how an English language dicationary works. Keys are words and definitions are values.) The keys in the dictionary should be Scheme Symbols and the values can be any type (as well as different types). Also add input error checking to your proceedure (that is verify that the dictionary is a list of pairs where the first element in the pair is a symbol).Submission: Submit a scheme file containing your code on the course blackboard site.