In a certain code language, 'PLANT' is written as 'QMAMS' and 'TREES' is written as 'USEDR'. How will 'SHRUB' be written in that language?

Let's trace the pattern for PLANT $\to$ QMAMS:P (+1) $\to$ QL (+1) $\to$ MA (-0) $\to$ AN (-1) $\to$ MT (-1) $\to$ SLet's crosscheck with TREES $\to$ USEDR:T (+1) $\to$ UR (+1) $\to$ SE (-0) $\to$ EE (-1) $\to$ DS (-1) $\to$ RThe pattern of shifts is clearly: [+1, +1, 0, -1, -1]Let's apply this pattern to SHRUB:S (+1) $\to$ TH (+1) $\to$ IR (-0) $\to$ RU (-1) $\to$ TB (-1) $\to$ AThus, the code for SHRUB is TIRTA.