The English alphabet contains 26 letters (a, b, c, ...y, z).
The digits from 0 to 9 are a total of 10.
A keycode contains 2 letters, and 3 numbers, for example:
AB 598; MM 139; NT 498; ...
So there are 26 possible choices for the first letter, which can combined with any of the 26 possible choices for the second letter, so there are a total of
26*26=676 possible pairs of letters.
Similarly, the 10 possible choices for the first number, which can be combined with the 10 possible choices for the second number, and the 10 possible choices for the third number make a total of :
10*10*10=1,000 possible triples of numbers.
Any of the 676 possible pairs of letters can be combined with any of the possible 1,000 triples of numbers. This makes a total of
676*1,000=676,000 keycodes.
Answer: 676,000
A graph that has no breaks in it is called a continuous data

Above, I changed the fraction form of x and y into exponential form so it is easier to see the differentiation. Now, we can differentiate:

Now that we have dy/dx, we can plug in the x, which is 4, and the y, which is 4/19. We know these values of x and y because your question stated y(4) = 4/19.
If I understand what you are asking, the number 5 is prime. The definition for a prime number is a number that has no factors other than itself and one. The prime factorization of 5 is 5 * 1. Since 5's factors are only itself and 1, that means that it is prime. The definition of a composite number is a number that has at least one divisor other than one and itself. This means that a number cannot be both prime and composite.