$6.$ Assume that a given plasmid vector to be used in a cloning experiment contains $4000$ base pairs of DNA. Assume also that the restriction endonuclease Cuj cuts this plasmid at the following sites $($starting from an arbitraty zero point$)$: $1000,1500,$ and $3000.$ Given complete digestion of the plasmid with the endonuclease so that only linear fragments are produced, what sizes of DNA are expected? $(4$ pt$)$