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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def terra(latitude, longitude, elevation, gast):
 """Compute the position and velocity of a terrestrial observer. `latitude` - Latitude in radians. `longitude` - Longitude in radians. `elevation` - Elevation above sea level in au. `gast` - Hours of Greenwich Apparent Sidereal Time (can be an array). The return value is a tuple of two 3-vectors `(pos, vel)` in the dynamical reference system (the true equator and equinox of date) whose components are measured in au with respect to the center of the Earth. """

    zero = zeros_like(gast)
    sinphi = sin(latitude)
    cosphi = cos(latitude)
    c = 1.0 / sqrt(cosphi * cosphi +
                   sinphi * sinphi * one_minus_flattening_squared)
    s = one_minus_flattening_squared * c
    ach = earth_radius_au * c + elevation
    ash = earth_radius_au * s + elevation

    # Compute local sidereal time factors at the observer's longitude.

    stlocl = 15.0 * DEG2RAD * gast + longitude
    sinst = sin(stlocl)
    cosst = cos(stlocl)

    # Compute position vector components in kilometers.

    ac = ach * cosphi
    acsst = ac * sinst
    accst = ac * cosst
    pos = array((accst, acsst, zero + ash * sinphi))

    # Compute velocity vector components in kilometers/sec.

    vel = ANGVEL * DAY_S * array((-acsst, accst, zero))

    return pos, vel