def PQKtoRST(coor_pqk):
    """From pqk base hextrahedron coordinate
    to rst base tetrahedron coordinate"""

    p,q,k = coor_pqk[0], coor_pqk[1], coor_pqk[2]
    r = (1+p)/2.0
    s = (1-p)*(1+q)/4.0
    t = (1-p)*(1-q)*(1+k)/8.0
    jac = (1-p)*(1-p)*(1-q)/64.0

    return r,s,t,jac